﻿838 
  Prof. 
  R. 
  W. 
  Wood 
  on 
  Resonance 
  

  

  fainter 
  companion 
  lines 
  are 
  scarcely 
  reduced 
  in 
  intensity 
  at 
  

   all. 
  This 
  shows 
  us 
  that 
  the 
  resonance 
  lines 
  do 
  not 
  all 
  

   coincide 
  with 
  absorption 
  lines, 
  or 
  at 
  least 
  that 
  their 
  intensities 
  

   are 
  not 
  proportional. 
  It 
  also 
  explains 
  the 
  comparative 
  

   weakness 
  of 
  line 
  6 
  of 
  the 
  first 
  order 
  group 
  in 
  the 
  case 
  of 
  

   stimulation 
  by 
  the 
  Cooper-Hewitt 
  lamp, 
  for 
  in 
  this 
  case 
  

   we 
  have 
  the 
  factor 
  of 
  absorption 
  in 
  operation 
  on 
  account 
  of 
  

   the 
  long 
  tube 
  used 
  in 
  the 
  experiment. 
  The 
  difference 
  in 
  the 
  

   appearance 
  of 
  the 
  4th 
  and 
  5th 
  order 
  groups 
  in 
  the 
  two 
  cases 
  

   cannot 
  be 
  explained 
  in 
  this 
  way, 
  however, 
  for 
  there 
  appears 
  

   to 
  be 
  no 
  selective 
  absorption 
  of 
  the 
  lines 
  of 
  these 
  groups, 
  as 
  is 
  

   shown 
  by 
  the 
  photographs. 
  We 
  are 
  therefore 
  forced 
  to 
  

   the 
  conclusion 
  that 
  the 
  stimulation 
  is 
  not 
  the 
  same 
  in 
  the 
  two 
  

   cases, 
  and 
  I 
  am 
  of 
  the 
  opinion 
  that 
  in 
  the 
  case 
  of 
  the 
  quartz 
  

   lamp 
  at 
  35 
  volts 
  absorption 
  line 
  4 
  is 
  excited 
  to 
  some 
  extent, 
  

   while 
  in 
  the 
  case 
  of 
  the 
  Cooper-Hewitt 
  lamp 
  the 
  excitation 
  is 
  

   confined 
  to 
  line 
  3. 
  This 
  is 
  confirmed 
  by 
  the 
  photographs 
  

   which 
  I 
  have 
  made 
  of 
  the 
  green 
  line 
  of 
  the 
  two 
  lamps 
  during 
  

   the 
  past 
  summer. 
  It 
  should 
  be 
  observed 
  also 
  that 
  in 
  the 
  

   case 
  of 
  the 
  Cooper-Hewitt 
  excitation 
  companion 
  line 
  No. 
  1 
  

   appears 
  in 
  the 
  first 
  and 
  third 
  order 
  groups. 
  In 
  the 
  case 
  of 
  

   the 
  quartz 
  lamp, 
  this 
  line 
  does 
  not 
  appear 
  until 
  the 
  potential 
  

   at 
  which 
  the 
  lamp 
  is 
  operated 
  is 
  increased 
  to 
  100 
  volts 
  or 
  

   over. 
  From 
  observations 
  of 
  many 
  photographs 
  I 
  am 
  inclined 
  

   to 
  refer 
  this 
  line 
  to 
  the 
  stimulation 
  of 
  an 
  absorption 
  line 
  

   marked 
  on 
  the 
  photograph 
  (PI. 
  XVI. 
  fig. 
  5) 
  which 
  is 
  in 
  

   coincidence 
  with 
  the 
  component 
  of 
  the 
  mercury 
  line 
  which 
  has 
  

   the 
  shortest 
  wave-length, 
  and 
  which 
  is 
  well 
  shown 
  in 
  fig. 
  6. 
  

   This 
  component 
  is 
  more 
  conspicuous 
  in 
  the 
  light 
  of 
  the 
  C.-H. 
  

   lamp 
  thau 
  in 
  the 
  case 
  of 
  the 
  quartz 
  one. 
  

  

  If 
  the 
  potential 
  of 
  the 
  quartz 
  arc 
  is 
  raised 
  to 
  46 
  volts 
  the 
  

   green 
  line 
  broadens 
  and 
  completely 
  covers 
  absorption 
  line 
  3, 
  

   and 
  nearly 
  covers 
  line 
  4, 
  stimulating 
  it 
  on 
  its 
  edge 
  of 
  shorter 
  

   wave-length 
  so 
  to 
  speak. 
  It 
  has 
  not 
  yet 
  been 
  ascertained 
  

   whether 
  the 
  resonance 
  spectrum 
  varies 
  according 
  to 
  whether 
  

   the 
  exciting 
  line 
  has 
  exactly 
  the 
  same 
  frequency 
  as 
  that 
  of 
  

   the 
  absorption 
  line, 
  or 
  one 
  slightly 
  different, 
  that 
  is 
  strikes 
  

   the 
  absorption 
  line 
  on 
  one 
  edge 
  only. 
  This 
  is 
  an 
  extremely 
  

   important 
  point, 
  and 
  I 
  hope 
  eventually 
  to 
  find 
  some 
  way 
  of 
  

   controlling 
  matters 
  so 
  that 
  the 
  question 
  can 
  be 
  answered. 
  

   For 
  the 
  present, 
  however, 
  I 
  am 
  obliged 
  to 
  assume 
  that 
  it 
  

   makes 
  no 
  difference. 
  

  

  The 
  strong 
  stimulation 
  of 
  absorption 
  line 
  4 
  appears 
  to 
  give 
  

   rise 
  to 
  the 
  companion 
  line 
  No. 
  2 
  of 
  the 
  groups. 
  With 
  60 
  

   volts 
  potential 
  difference, 
  line 
  4 
  makes 
  its 
  appearance 
  in 
  the 
  

  

  